1. Field of the Invention
This invention relates to zoom lenses suited to a single-lens reflex camera, video camera, etc. and, more particularly, to a zoom lens, while including the wide-angle region, having an extremely high variable magnification range of as much as 10.
2. Description of the Related Art
The zoom lenses including focal lengths of from the wide-angle to the telephoto region are known in, for example, Japanese Laid-Open Patent Applications No. Sho 57-164710 and No. Sho 60-39613. In these publications, zoom lenses composed of five units of plus, minus, plus, minus, plus, when counted from the object side, are obtained with a zoom ratio of 3 to 5.
Meanwhile, in Japanese Laid-Open Patent Application No. Hei 1-191819, likewise with the 5-unit form of plus, minus, plus, minus, plus, a zoom lens having a zoom ratio of about 10 is disclosed.
However, the above-described zoom lenses have their diameters of the front lens members (the first lens unit) and their total lengths of the optics (the distance from the first lens surface to the image plane) to get relatively large. Further, in particular, Japanese Laid-Open Patent Applications No. Sho 57-164710 and No. Sho 60-39613 are low in the zoom ratio, and could not be said to be sufficient, as, in recent years, a zoom lens having a higher zoom ratio is demanded. In Japanese Laid-Open Patent Application No. Hei 1-191819, a zoom lens of a remarkably high zoom ratio is disclosed, but the total length of the optics is long and the diameter of the front lens members, too, is considerably large.